Method for forming tubular metal articles



March 17, 1959 R; J. wn cox 2,877,546

METHOD FOR FORMING TUBULAR METAL ARTICLES Filed June 9. 1953 INVENTRAYMOND J. WIL 0 -AIT0RNEY5 Z5 Sheets-Sheet 1 :3

March 17, 1959 R. J. WILCOX 2,877,546

METHOD FOR FORMING TUBULAR METAL ARTICLES Filed June 9. 1953 3Sheets-Sheet 2 III I I ///l ETU INVENTO RAYMOND J. WlL BY FIG. 2

ATTORNEYS METHOD FOR FORMING TUBULAR METAL ARTICLES- Filed June 9. 1953R. J. WILCOX March 17, 1959 3 Sheets-Sheet 3 7 ll/IF I I! I If! FIG.

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ATTORNEYS United States Patent METHOD FOR FORMING TUBULAR METAL ARTICLESRaymond J. Wilcox, Lansing, Mich., assignor to Motor Wheel Corporation,Lansing, Mich, a corporation of Michigan Application June 9, 1953,Serial No. 360,532

3 Claims. (Cl. 2--544) This invention relates to a method for formingtubular metal articles by fashioning and shaping fiat metal stock. Themaking of ordnance shells and particularly rocket heads exemplifies theinvention, although it may be employed in making other tubular metalarticles.

A rocket head is generally tubular and has a tapered shape, beingsmallest at its nose or leading end and largest at its trailing end. Inaccordance with the invention the metal blank is first formed into asubstantially cylindrical tubular shape and is thereafter subjected to aradial expansion to provide the tapered shape. The extent of theexpansion varies axially of the hollow blank and the thickness of thewall of the blank, because of the flow requirements of the metal, isreduced to an extent generally proportional to the extent of theexpansion. Expansion of the cylindrical blank without intermediateconditioning would therefore result in the wall being relatively thickat the end of the lesser expansion and relatively thin in zones ofgreater expansion.

It is an object of the invention to provide a method for so working thecylindrical tubular workpiece as to prevent undue variation of Wallthickness between regions of maximum and minimum expansion. To this end,the cylindrical tubular workpiece is subjected to a punch and dieoperation wherein its tubular wall is simultaneously elongated andvaried in thickness in a manner keyed to the nature of the radialexpansion to which the workpiece is to be subjected, so that theexpanded article may have, as desired, a wall thickness which issubstantially uniform from one end to the other or which is non-uniform.If, for example, the article to be formed tapers substantially uniformlyin shape from one end to the other, the thickening of the wallpreparatory to the radial expansion may also be substantially uniform.one embodiment of the invention is shown in the accompanying drawings:

Fig. 1 is a view largely in section showing a punch press and a reversetapered punch with a blank or workpiece thereon, the press being shownat the bottom of the work stroke.

Fig. 2 is partly in section showing a blank positioned to be forcedthrough a die by the reverse tapered punch shown in elevation.

Fig. 3 is similar to Fig. 2 but showing the workpiece after it has beenpassed through the die and stripped from the punch.

Fig. 4 is in section showing a blank from which the rocket head may befashioned.

Fig. 5 shows the blank after a coining operation.

Fig. 6 shows the blank after a cupping operation.

Fig. 7 shows the blank after a first reduction.

Fig. 8 shows the blank of Fig. 7 with the nose indented and the interiorbottom wall flattened by a pressing operation.

Fig. 9 is in section showing the blank of Fig. 8 after it has been drawnand expanded by the method of this invention, and showing the taperedwall structure.

Fig. 10 shows the blank of Fig. 9 after the upper end has been trimmedand the nose has been pierced.

Fig. 11 shows the blank slightly expanded.

Fig. 12 shows the blank after the nose has been tapered inwardly. Fig.13 shows the expanded completed rocket head.

A blank 1 (Fig. 4) is coined into a dish like shape 2 (Fig. 5) havingsloping sides 3 and a generally flat bottom portion 4. The blank 2 isthen cupped, giving it the form shown at 5 in Fig. 6 wherein the sidewall 6 is cylindrical. The blank 5 is subjected to a first reductionwhich elongates the cylindrical wall to the form shown at 7 in Fig. 7.In a pressing operation the exterior of the bottom portion of the blank7 is indented as shown at 8 (Fig. 8) and the interior bottom surface isflattened as shown at 9 thereby forming the workpiece shown at 10 whichhas a cylindrical wall 11. The operations thus far described areperformed by conven-- tional processes and by suitable apparatus.

The workpiece 10 is then subjected to a second reduction and anexpansion by the method of this invention which is best illustrated bythe reference to Figs. 1, 2 and 3.

A punch press, shown in Fig. 1, has a movable head 15 with a punchholder 16 secured thereto by means of a retainer ring 17. A punch 18 issecured to the punch holder as shown. The lower or leading end 19 of thepunch is adapted to fit the interior end 9 of the workpiece 10. Thepunch has a round cross section and has a reverse taper, being largestat a location generally indicated at 20 near its leading end and beingsmallest at a loction indicated at 21 near its upper end or base.- Thepunch may have a vent 22 opening to the atmosphere to facilitatestripping'of a workpiece therefrom.

The punch press table 25, by means of a support 26, supports a frame 27upon which is mounted a member 28 embodying one or more strippers 29.The strippers are hinged as shown and yieldably held into position bysprings 30 so that they may be moved to one side during the down strokeof the punch and so that they will snap back into stripping positionafter the workpiece has cleared them.

A die ring 31 is mounted on the member 28 and holds the die 32 in properposition. The drawing surface of the die is shown at 33. A guide ring 34is provided for guiding the punch and the various members are secured inplace by a clamp plate 35.

In operation, a workpiece 10 is disposed within the guide bushing 34 andin axial alignment with the annular die 32 as shown in Fig. 2. In thedownstroke of the punch the end 19 thereof engages the interior endsurface 9 of the workpiece and draws the workpiece through the diethereby elongating the wall 11 of the workpiece. Because of the reversetaper of the punch, the interstice between the surface thereof and thedrawing surface 33 of the die gradually increases during the down strokeof the punch. The metal of the wall 11 is forced by the die to flow intoand fill the interstice and thus forms the thickening wall of theworkpiece as shown, which in the form shown is thickest at the upper endportion. As shown in Fig. 1, the workpiece has a cylindrical exteriorwhile the interior surface tapers inwardly, fitting the taper of thepunch.

During the work stroke of the punch, the workpiece pushes the hingedstrippers 29 out of its path. The work stroke continues until theworkpiece has cleared both the die and the strippers, whereupon thestrippers snap back into horizontal position under action of the springs30. The strippers are prevented by the die ring 31 from'rotating beyondthe horizontal. During the up stroke of the punch the strippers catchthe upper end face 36 of the 3 workpiece and prevent its further upwardmovement, whereby it is stripped from the punch 18.

After the drawing operation and before the stripping operation the lowerend portion 20 of the punch has a diameter, greater than the innerdiameter of portions of the workpiece above it. Hence the strippingexpands the wall of the workpiece, thereby forming the workpiece shownin Fig. 9 which has a generally cylindrical interior surface and anexterior surface which tapers outwardly toward the upper, or trailing,end (Fig. 9). The interior surface may not be exactly cylindricalbecause the wall of the workpiece will tend to spring back somewhatfollowing the expansion.

The workpiece in the form shown in Fig. 9 may now'be fashioned into afinished article by a number of steps such as those indicated in Figs.10, ll, 12 and 13. After the open end of the workpiece has been trimmedand the closed end has been pierced to provide the opening 37 (Fig. 10),the workpiece may be expanded to the form shown in Fig. 11 with aconsequent thinning and axial shortening of the walls thereof because ofthe flow requirements of the metal. The nose portion of the workpiece isthen tapered inwardly as by a swaging operation to the form shown inFig. 12. Finally the workpiece is subjected to an expanding operation,which is again attended by a shortening and thinning of the walls, togive it the form shown in Fig. 13. The workpiece is annealed whenevernecessary during the course of being worked.

While the finished article may have a wall thickness substantiallyuniform from one end to the other, the thickness may be varied asrequired to give it the necessary strength in desired zones. As shown inFig. 13, for example, the side wall of the article is slightly thickeradjacent the flared open end than at the portion spaced approximatelymidway between the ends of the article. More generally, it is to beappreciated that by varying the shape of the punch, the extent, shapeand location of the taper of thickness of the wall of the workpiece maybe varied; hence, by the method of this invention workpieces may be madewhich are adapted to be expanded or otherwise fashioned into articles ofmany and varying shapes.

Such terms as up, down, horizontal, etc. are used herein merely asconvenient terminology and not as delimitations,

What I claim is:

1. In a method of forming from a cup-shaped work piece having a sidewall of substantially uniform thickness and having a bottom wall, atubular article having tapered form and also having a side wall ofsubstantially uniform thickness, the steps of subjecting the work pieceto a drawing operation to elongate the work piece and vary the thicknessof the side wall axially of the work piece so that said side wall isthicker adjacent the open end of said work piece than adjacent saidbottom wall, and after said drawing operation trimming said open end ofsaid work piece, forming a central opening in said bottom wall, taperingthe closed end portion of the work piece inwardly so that the diametersof said bottom wall and said opening are reduced, and expanding the openend portion of the work piece into tapered form with the extent ofexpansion varying generally proportionally to the variation of thethickness of the side wall whereby the side wall provides metal tocompensate for the thinning thereof incident to expansion.

2. In a method of forming, from a tubular work piece having a wall ofsubstantially uniform thickness, a tubular article having tapered formand also having a wall of sub stantially uniform thickness, the steps ofsubjecting the tubular work piece to a drawing operation to elongate thework piece and decrease the inner diameter of at least a portion of thework piece to an extent varying axially of the work piece whilemaintaining the outer diameter of the work piece substantially uniform,then subjecting said work piece to a first radial expansion in which theinterior of said portion of the work piece is expanded to substantiallycylindrical form of a diameter substantially equal to the largestdiameter of said portion following said drawing operation, and thensubjecting said work piece to additional radial expansion to expand thework piece both internally and externally to tapered form with theextent of the radial expansion varying generally proportionally tothevariation of the thickness of the wall resulting from said first radialexpansion, whereby the wall provides metal to compensate for thethinning thereof incident to said second expansion step.

3. In a method of forming, from a tubular work piece having a wall ofsubstantially uniform thickness and having an open end and a closed end,a tubular article having tapered form and also having a wall ofsubstantially uniform thickness, the steps of subjecting the tubularwork piece to a drawing operation to elongate the work piece anddecrease the inner diameter of at least a portion of the work piece toan extent varying axially of the work piece while maintaining the outerdiameter of the work piece substantially uniform so that said wall isthicker adjacent said open end than adjacent said closed end, and aftersaid drawing operation subjecting the work piece to a first radialexpansion in which the interior of said portion of the work piece isexpanded to substantially cylindrical form, of a diameter substantiallyequal to the largest diameter of said portion following said drawingoperation, trimming said open end of said work piece, forming a centralopening in said closed end, tapering said closed end inwardly so thatthe diameters of said closed end and said opening therein are reduced,and subjecting said portion of said work piece to additional radialexpansion to expand the work piece to tapered form with the extent ofexpansion varying generally proportionally to the variation of thethickness of the wall whereby the wall provides metal to compensate forthe thinning thereof incident to expansion.

References Cited in the file of this patent UNITED STATES PATENTS273,924 Whiting Mar. 13, 1883 274,356 McDougall Mar. 20, 1883 598,800Meyer Feb. 8, 1898 1,295,430 Carlson Feb. 25, 1919 1,387,924 Deneen Aug.16, 1921 1,412,794 Penfield Apr. 11, 1922 1,756,416 Woodhead Apr. 29,1930 1,886,210 Mitchell Nov. 1, 1932 1,925,823 Singer Sept. 5, 19332,024,285 Handler Dec. 17, 1935 2,024,286 Handler Dec. 17, 19352,360,353 Lyon Oct. 17, 1944

